On 25 October 2011 20:34, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > Aha! OHCI controllers from NVIDIA are known to have some weird bugs. > The kernel tries to work around them, but it doesn't always do a > perfect job. > > Below is a patch you can try out. It won't fix the problem directly, > but it will create two new sysfs files for you. After you boot the new > kernel, but before attaching the modem, look at: > > /sys/bus/pci/devices/0000:00:02.0/shutdown_quirk > /sys/bus/pci/devices/0000:00:04.0/shutdown_quirk > > I expect each of them will contain a 0. Try writing a 1 into each and > then see how the modem behaves. Thanks Alan. I tried the fix that you provided on 3.0.4 version of the kernel, but it did not quite work as expected. I could see these two sysfs files, and their value was 0 as you expected. However changing the value to 1 made no difference as far as the USB modem is concerned. It continues to connect and disconnect regularly. Further, I did try the other modem that was working before, and it continues to work even after application of this patch. Another noticeable thing is the complete absence of "unable to enumerate USB device" message in the dmesg output. I have attached usbmon logs after application of the patch (if it helps). The dmesg output (same as before): [ 659.529977] usb 3-2: new full speed USB device number 24 using ohci_hcd [ 659.734814] scsi18 : usb-storage 3-2:1.0 [ 664.831694] usb 3-2: USB disconnect, device number 24 [ 665.559981] usb 3-2: new full speed USB device number 25 using ohci_hcd [ 669.274840] usb 3-2: USB disconnect, device number 25 [ 671.426632] usb 3-2: new full speed USB device number 26 using ohci_hcd [ 671.631504] scsi19 : usb-storage 3-2:1.0 [ 676.735364] usb 3-2: USB disconnect, device number 26 [ 677.473296] usb 3-2: new full speed USB device number 27 using ohci_hcd [ 681.188466] usb 3-2: USB disconnect, device number 27 [ 683.339962] usb 3-2: new full speed USB device number 28 using ohci_hcd [ 683.544892] scsi20 : usb-storage 3-2:1.0 [ 688.645222] usb 3-2: USB disconnect, device number 28 I am not sure if this points to anything or not, but the in the above dmesg output, scsi device detection does not occur with each USB device connect/disconnect cycle. -OBD
Attachment:
usbmon.log.gz
Description: GNU Zip compressed data
